1. Field of the Invention
The present invention relates to a surface emitting laser element that includes an active layer and a dielectric multilayer mirror and a method of fabricating the surface emitting laser element.
2. Description of the Related Art
A vertical cavity surface emitting laser (VCSEL) element has been used as a light source for optical communications such as an optical interconnection or a device for various applications (see, for example, Japanese Patent Application Laid-open No. 2004-207380). A plurality of VCSEL elements can be arranged in a two-dimensional array on a single substrate more easily than edge-emitting laser elements, because each VCSEL element emits a laser light in the vertical direction with respect to the substrate. Moreover, the VCSEL element has preferable properties, due to a compact-sized active layer, such as extremely low threshold current and laser oscillation at low consumption power.
In a typical VCSEL element, a distributed Bragg reflector (DBR) mirror is used in a resonator. It has been widely known that a DBR mirror formed with a plurality of dielectric layers having different refractive indices (hereinafter, “dielectric DBR mirror”) can reduce optical absorption loss, so that it is possible to obtain a high-power laser source. There have been developed VCSEL elements including the dielectric DBR mirror in a resonator (see, for example, Japanese Patent Application Laid-open No. 2004-103754). Reflectance of the dielectric DBR mirror depends on the number of dielectric layers, and therefore laser output characteristics of the VCSEL element including the dielectric DBR mirror depends on the number of the dielectric layers.
However, the reflectance of the dielectric DBR mirror changes by a large amount with increase or decrease of the number of dielectric layers, because the refractive index difference between of the dielectric layers is large. This makes it difficult to obtain a dielectric DBR mirror with desired reflectance. Therefore, it is difficult to fabricate a VCSEL element including the dielectric DBR mirror in the resonator with desired laser output characteristics.